Walmart workers have hailed their wage protest, saying their walkout on "Black Friday" had shown the world's largest retailer their determination to fight against all odds.

Hundreds of protesters targeted Walmart stores across the United States on Friday, the busiest shopping day of the year, accusing the bargain superstore of ripping off its own employees.

The protests were designed to disrupt the Black Friday shopping frenzy, after Thursday's Thanksgiving holiday, when deep discounts pull in waves of customers.

"Today's protests at Walmart stores across the country are a reminder of the enormous power of working people uniting to demand a better future with a living wage, affordable healthcare and respect on the job," said Mary Kay Henry, president of the 2.1 million-member Service Employees International Union (SEIU).

Her optimism was shared by Colby Harris, a Walmart sales associate who walked off his job in Lancaster, Texas late on Thursday.

"Our voices are being heard," said Harris. "And thousands of people in our cities and towns and all across the country are joining our calls for change at Walmart. We are overwhelmed by the support and proud of what we've achieved so quickly and about where we are headed."

The main force behind the wage protest, the Organisation United for Respect at Walmart (OUR Walmart), said it was pressuring for "decent pay, regular hours, affordable healthcare and respect."

The powerful UAW auto-workers union also came on board, saying that because of Walmart's size, the company "has enormous power to set the trends not just for the retail and service industries, but for the economy as a whole."

Another prominent supporter was Robert Reich, labour secretary under president Bill Clinton, who saw the debate over conditions at Walmart, owned by the multi-billionaire Walton family, as reflecting deeper problems in US society.

"The widening inequality reflected in the gap between the pay of Walmart workers and the returns to Walmart investors, including the Walton family, haunts the American economy," Reich wrote in a post to his blog titled, Why You Shouldn't Shop at Walmart on Friday.

Walmart, which denies there are any widespread complaints, last week filed a complaint with the National Labor Relations Board to try to block the Black Friday protests.

On Friday, the retail giant downplayed the controversy, saying in a statement that "only 26 protests occurred at stores last night and many of them did not include any Walmart associates."

In addition, Walmart US said it had its "best ever Black Friday events," featuring 1.8 million towels, 1.3 million televisions and 1.3 million dolls sold in the first hours.

About 200 activists outside a huge Walmart in Secaucus, New Jersey chanted against what they called the dark side of the biggest US private employer, which has 1.3 million non-unionised workers, or "associates," as they're called. Critics say the average Walmart hourly wage is a meagre $US8.81 ($A8.53), although the company says the figure is closer to $US13. ($A12.58)

"Walmart pushes wages down!" they chanted.

Protesters included unionised workers, street activists from the Occupy movement, a roller-skating woman in a Marie-Antoinette mini-dress, a faux pastor known for his anti-capitalist campaigns, and a lively brass band.

The protesters, however, did not appear to include any employees from the Walmart outlet, where the doors were open to a steady stream of shoppers, many re-emerging with shopping carts piled high.

Jaclyn Kessel, one of the organisers of the demonstration, said Walmart employees "are afraid of getting fired" and she didn't expect any to come.

In Los Angeles, nine protesters were arrested for blocking an intersection in front of a Walmart in Paramount, local media reported. About 400 people gathered for that protest, the LA Daily News said, citing police estimates.

In Secaucus, shoppers had to negotiate an increasingly thick crowd of protesters in the entrance, many of whom were dancing to the brass band, watched by a half dozen patient police officers.

Drivers in several passing cars tooted horns in support, but most paid no attention to the disturbance.

Karen Mendoza, 30, expressed sympathy with the protesters as she went into Walmart with her 55-year-old mother, saying that the kind of low-end jobs the store offers are part of an increasingly unforgiving economy.

"With the economy today it's really, really hard to get a job anywhere," she said. "My mother works at a factory. She's been there for 27 years, and they're getting rid of people all the time."

"I'm here to support the low-wage worker," she said. "Basically, unless you come from money and have access, there's very little social mobility in America," Halasa, 46, said, before gliding away on her skates.